netdev - Re: [PATCH net-next 11/15]bnx2x: Add TPA, Broadcoms HW LRO

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Message-ID: <20080617151704.GK5350@solarflare.com>
Date:	Tue, 17 Jun 2008 16:17:06 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Eilon Greenstein <eilong@...adcom.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Michael Chan <mchan@...adcom.com>,
	Vladislav Zolotarov <vladz@...adcom.com>
Subject: Re: [PATCH net-next 11/15]bnx2x: Add TPA, Broadcoms HW LRO

Ben Hutchings wrote:
> Eilon Greenstein wrote:
> > The TPA stands for Transparent Packet Aggregation. When enabled, the FW
> > aggregate in-order TCP packets according to the 4-tuple match and sends
> > 1 big packet to the driver. This packet is stored on an SGL in which
> > each SGE is 1 page. The FW also implements a timeout algorithm and it
> > honors all TCP flag, including the push flag as a trigger to halt
> > aggregation.
> [...]
> 
> LRO is not compatible with forwarding and will currently trigger a BUG() or
> WARN() if used on packets that are then forwarded.

Actually, since this implementation doesn't set gso_size in LRO'd skbs, it
will confuse TCP in interesting ways instead.  You need to set gso_size to
the largest segment size seen in the packets that were aggregated.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
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